Solvent extraction of oils with dimethylammonium dimethylcarbamate



Patented Apr. 22, 1952 SOLVENT EXTRACTION F OILS WITH DIMETHYLAM'MONIUM DIMETHYLCAR- BAMATE Donald J. Loder, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing.

This invention relates to the treatment of mineral oils and more particularly to refining petroleum distillates by solvent extraction processes employing dimethylammonium dimethylcarbamate as an extractive solvent.

It is known that petroleum fractions contain undesired components such as sulfur compounds and unsaturated hydrocarbons. Selective solvents have heretofore been suggested for extracting such components. Furfural and liquid sulfur dioxide are perhaps the most favorably received of such solvents. The use of these materials, however, entails process complicating factors. For example, sulfur dioxide. must be used under pressure and furfural is rather difiicult to remove from the refined materials particularly if the refined material is a light distillate.

It is an object of this invention to provide solvent extraction processes for refining mineral oils which overcome the aforementioned disadvantages of the methods used heretofore. Another obiect is to provide methods for removing undesired components from petroleum distillates. A further object is to provide processes for removing unsaturated compounds, aromatic compounds and especially sulfur compounds from petroleum distillates. A still further object is to provide methods for improving the diesel index of fuel oils. Another object is to provide solvent extraction processes in which the solvent is readily separated from the refined petroleum distillate by extraction with water. Other objects will become apparent hereinafter.

The foregoing and other objects of the invention are attained by subjecting mineral oils to extraction by means of dimethylammonium dimethylcarbamate. vention are carried out by bringing a petroleum distillate into intimate contact in the liquid state with dimethylammonium dimethylcarbamate, forming an extract phase containing impurities dissolved in dimethylammonium climethylcarbamate and a raflinate phase containing refined petroleum distillate, and separating the two phases.

The processes of the invention are applicable to mineral oils and to all petroleum distillates, including gasoline, kerosene, fuel oil, and lubricating oil. The processes are particularly useful for the treatment of distillates obtained as a result of catalytic cracking and especially catalytically cracked fuel oil containing unsaturated compounds and sulfur compounds.

Dimethylammonium dimethylcarbamate, the extractant employed in the processes of the in- Thus processes of the in Application February 14, 1950, Serial No. 144,193

3 Claims. (01. 196-4435) vention, is a water-white liquid having an amine odor and the following physical properties:

The extraction is suitably carried out according to methods well known in the petroleum in dustry for effecting liquid-liquid contact in $01 vent extraction processes. Thus, the oil may be treated with one or more successive portions of the solvent, which portions may vary in size ac: cording to the degree of refining required' Al ternatively, the operation may be continuous by causing the oil and the solvent to flow countercurrent, as for example, thru a vertical extraction tower.

The ratio of dimethylammonium diniethylcar bamate to petroleum distillate employed in the processes of the invention will be varied widely depending upon the particular distillate used,

the efiiciency of the extraction method employed and the degree of refining desired. In general, good results will be obtained with solvent:distillate volume ratios from about 0.1:1 to 41:1.

The temperature at which the extraction step is carried out may be varied depending on the physical and chemical characteristics of the material treated. The use of ordinary or ambient temperatures gives good results in most cases. In some cases, better results will be obtained using lower temperatures, say down to 32 F. or below, while in others, as when the distillate is viscous or solid at normal temperatures, the extraction may suitably be carried out at temperatures up to the atmospheric boiling point of dimethylammonium dimethylcarbamate (140.3" E), or even higher by use of pressure.

Changes in the relative solvent action of dimethylammonium dimethylcarbamate on components of petroleum distillates are realized by varying the temperature.

Following the intimate mixing of the solvent and the distillate oil in the extraction step, the mixture is separated into extract and rafflnate phases. The extract phase contains impurities dissolved in the main body of the solvent; the rafiinate phase contains the treated improved distillate and generally a small portion of the solvent.

The solvent is removed from the separated phases according to conventional methods. For example, the solvent may be suitably separated and recovered by distillation or alternatively by washing the phases with water in which dimethylammonium dimethylcarbamate is extremely soluble.

As a specific example, a catalytically cracked 'fuel oil was extracted with dimethylammonium Charge Raliinate Extract Gravity at 60(60" F., "API 30.7 i 33.3 13.2 Spec fic Gravity at 60/60 F 0872 5 0.859 0.978 Aniline Point, F 128.5 140.9 -4 Diesel Index No 39.5 46.9 -O.5 Total Su1fur,.we1ght per cent. 0.66 i 0.46 1.8

The above data show marked refining of the fuel oil by the single treatment. The sulfur content was reduced and important increase in the parafiinic character of the oil is indicated by the increase in API gravity and aniline point and the decrease in specific gravity. The non-- parafiinic character of the extract is shown by avery low aniline number and high specific gravity. The Diesel index number (the aniline point multiplied by the API gravity at 60 F. and divided by 100) which is Widely used as a measure of ignition quality is much improved by the refining operation.

In a similar test in which a West Coast gasoline: was used as the petroleum distillate, the raflinate comprised about 83.5% by volume of the recovered petroleum distillate, and the following data were obtained on the original distillate, the raffinate and the extract:

The results show especially the value of dimethylammonium dimethylcarbamate in removing sulfur compounds from the fuel.

I claim:

1. A process for refining a mineral oil which comprises subjecting the oil in liquid state to extraction by means of dimethylammonium dimethylcarbamate whereby an extract phase and a raffinate phase are obtained, and separating the two phases.

2. A process for refining a petroleum distillate which comprises bringing the distillate into intimate contact in the liquid state with dimethylammonium dimethylcarbamate, forming an extract phase containing extracted impurities dissolved in the dimethyl'ammonium dimethylcarbamate and a raffinate phase containing refined petroleum distillate, and separating the two phases.

3. A process for refining a catalytically cracked fuel oil which comprises bringing the fuel oil into intimate contact in a liquid state with dimethylammonium dimethylcarbamate, forming an extract phase containing extracted impurities dissolved in the dimethylammonium dimethylcarbamate and a rafiinate phase containing refined fuel oil, and separating the two phases.

DONALD J. LODER.

REFERENCES CITED UNITED STATES PATENTS Name Date Taveau July 2, 1918 Number 

1. A PROCESS FOR REFINING A MINERAL OIL WHICH COMPRISES SUBJECTING THE OIL IN LIQUID STATE TO EXTRACTION BY MEANS OF DIMETHYLAMMONIUM DIMETHYLCARBAMATE WHEREBY AN EXTRACT PHASE AND A RAFFINATE PHASE ARE OBTAINED, AND SEPARATING THE TWO PHASES. 